A terbium-sensitized spectrofluorimetric method for determination of catecholamines in a serum sample with micelle medium

A terbium-sensitized spectrofluorimetric method has been developed for determination of catecholamines such as norepinephrine (NE), epinephrine (EP) and dopamine (DA), using sodium dodecyl benzene sulphonate (SDBS). Fluorescence sensitization of terbium ions (Tb(3+) ) by complexation with catecholamines in the presence of SDBS was observed. The fluorescence intensities of the Tb(3+) -catecholamine complexes were highly enhanced by introducing SDBS with an emission maximum at 545 nm after excitation at 290 nm. The conditions for the complex formation of Tb(3+) -catecholamine were investigated systematically and optimized to determine catecholamines in a serum sample. Under the optimum conditions, the fluorescence intensities of the Tb(3+) -catecholamine complexes were increased linearly with the concentration of NE, EP and DA over the ranges 2.5 × 10(-10) -1.0 × 10(-8) , 2.5 × 10(-10) -1.0 × 10(-8) and 2.5 × 10(-9) -1.0 × 10(-7) g/mL with correlation coefficients of 0.999, 0.999 and 0.9996, respectively. The limits of detection (3δ) of NE, EP and DA were found to be 4.6 × 10(-11) , 7.8 × 10(-11) and 8.38 × 10(-10) g/mL, respectively. Precision of the method was tested at the concentration level of 1.2 × 10(-7) g/mL for five replicate measurements of NE, EP and DA, giving relative standard deviations (RSDs) of 1.41%, 1.23% and 1.89%, respectively. The interaction mechanism of the Tb(3+) -catecholamine complexes system was investigated and presented with ultraviolet absorption spectra. The proposed method has been applied for the quantitative determination of NE, EP and DA in a spiked serum sample and a pharmaceutical preparation sample.